Say you write to your MP, saying 'please don't legalise hunting'. Your MP would send that letter on to DEFRA for a reply. One of the Ministers there needs to have it in their portfolio, so there's someone to write back saying 'we have no plans to at present', or whatever.

DEFRA would know what the plans were either way,if you wrote and asked. In fact they DEFRA website says, of the hunting act:

"It is flawed, illiberal and unenforceable."

We've been dealing with it for years without needing someone who has it in their job description. You'd only need to have someone formally responsible for it if you intended to make a policy change and please the pro-hunt lobby. This is what they want to do. Everyone knows they're going to have a free vote on it as soon as they think they can get it through parliament.